July 15, 2011 2:48pm EDTJuly 14, 2011 6:40pm EDTPittsburgh allowed the fewest big plays in the NFL last season, thanks in large part to safety Troy Polamalu. Vinnie Iyer examines the Steelers and other successful teams.

You know a big play in the NFL when you see it. But officially, according to STATS, it's defined as a play that gains 20 yards or more. Unofficially, it's an offensive strike that breaks the back of the opposition.

It can be demoralizing for a bend-but-not-break defense to give up a play that goes at least one-fifth the length of the field. When a player is allowed to get that far downfield in a matter of seconds, it naturally increases the potential to score points during the drive and improves that team’s chances of winning the game.

For teams that have built defenses to stop the big play, it takes consistent, strong fundamentals — a good pass rush, solid coverage and sure tackling — to succeed. Here's a breakdown of the 10 best teams at limiting big plays last season:

1. Pittsburgh Steelers (36 big plays allowed, 5 big-play TDs allowed)

2. San Diego Chargers (43, 5 TDs)

3. Atlanta Falcons (48, 9 TDs)

4. Minnesota Vikings (49, 9 TDs)

5. Tampa Bay Buccaneers (51, 9 TDs)

6. Green Bay Packers (54, 8 TDs

7. Kansas City Chiefs (54, 8 TDs)

8. Miami Dolphins (54, 12 TDs)

9. Buffalo Bills (54, 13 TDs)

10. Detroit Lions (54, 14 TDs)

• It's a bit of a surprise that only six of these teams finished .500 or better last season, but those six teams fall in the top seven on the list.

• The Steelers have the perfect formula to limit big plays. James Harrison and LaMarr Woodley get it started with an elite pass rush. There is solid tackling by the back seven, with Troy Polamalu covering a lot of ground, and physical play from the cornerbacks.

• Harrison and Woodley's team was No. 1, but the teams of fellow top-20 sack artists John Abraham, Jared Allen, Clay Matthews, Tamba Hali, Cameron Wake and Ndamukong Suh are also represented. Big plays require time to develop, so when an offense has to account for an elite pass rusher, that window shrinks.

• Clean-up tacklers are welcome. That's how the Bills made it, as linebacker Paul Posluszny and safety Donte Whitner (both free agents) combined for 291 total tackles last season. Joining Posluszny as prolific inside tacklers from teams on the list are the Steelers' Lawrence Timmons, the Bucs' Barrett Ruud and the Chiefs' Derrick Johnson.

• The Chargers have a great big-play differential. They ranked third in producing the most big plays, with 79 that accounted for 15 touchdowns.

Here’s a breakdown of the 10 teams that allowed the most big plays in 2010:

1. Denver Broncos (84 big plays allowed, 20 big-play TDs allowed)

2. Seattle Seahawks (76, 14 TDs)

3. Arizona Cardinals (74, 14 TDs)

4. Jacksonville Jaguars (72, 16 TDs)

5. Washington Redskins (70, 10 TDs)

6. Dallas Cowboys (69, 9 TDs)

7. Oakland Raiders (68, 18 TDs)

8. St. Louis Rams (66, 7 TDs)

9. Cincinnati Bengals (64, 15 TDs)

10. Philadelphia Eagles (63, 10 TDs)

• Of this group, only Seattle, with a sub-.500 record, and Philadelphia made the playoffs.

• The Broncos were smart to hire a defensive-minded head coach, John Fox, and get a high impact versatile defender, linebacker Von Miller, with their first draft pick. They gave up the most big-play runs and touchdowns (22, 8) last season.

• The Seahawks, Cardinals and Cowboys all had similar problems last year, as they got inconsistent and sometimes porous cornerback play. Although there are some talented playmakers in the secondary of each team, this year will be all about eliminating the big lapses in coverage.

• The Rams gave up a considerable amount of big plays, but what helped them stay in contention in the NFC West was limiting the touchdown damage from them.

• Despite a good pass rush and the presence of cornerback Nnamdi Asomugha, the Raiders gave up far too many big-play TDs — a big reason they settled for 8-8. That said, if the Eagles land Asomugha, it would easily erase them from the bottom 10 in 2011.

Team to watch

Minnesota Vikings. The Vikings had a little bit of an off season with their pass rush, but if they can re-sign Ray Edwards, he’ll continue to be a good complementary end to Allen. When it comes to the cover 2 defense that protects the deep halves of the field, few coaches are better using that scheme than Leslie Frazier. At weakside linebacker, Chad Greenway has become an absolute force. But if the Vikings lose Ben Leber as a free agent, they'll need to find an adequate replacement on the strong side.